Another good rule of thumb is that if you're ever in a position where you feel the need to assert that something is "obvious", it probably isn't.

All too often people try to end a debate by asserting that some point (from which their position inevitably follows) is "obvious". If it were obvious, they likely wouldn't be having the debate in the first place. It's much more likely that someone disagrees with the foundation of an argument than that they agree with the premises but are too stupid to see their consequences.